Roller cone drill bit with evenly loaded cutting elements

Abstract

A drill bit is used for drilling through earthen formations and forming a wellbore. The drill bit includes a bit body having a bit axis, and at least a first cone and a second cone coupled to the bit body. Each of the first and the second cones has a backface, a nose opposite the backface, and a cone axis of rotation. An array of cutting elements coupled to the first or second cones is in a band that lies between the backface and the nose. The cutting elements in the band are arranged at radial positions with respect to the bit axis and at least two adjacent cutting elements are at a same radial position within the array, and the remaining cutting elements are at different radial positions within the array.

What is claimed is: 
     
       1. A drill bit for drilling through earthen formations and forming a wellbore, the drill bit comprising:
 a bit body having a bit axis; 
 at least a first cone and a second cone coupled to the bit body, each of the first and the second cone having a backface and a nose opposite the backface; 
 a first array of first cutting elements coupled to at least one of the first or second cones between the backface and the nose, a tip of each first cutting element being located in one of a plurality of radial positions defined by a radial distance from the bit axis and a bottom hole depth relative to the bit axis, and a number of first cutting elements located at a first radial position having a maximum bottom hole depth within the first array being greater than a number of first cutting elements located at a second radial position having a lesser bottom hole depth within the first array; and 
 a second array of second cutting elements coupled to at least one of the first or the second cones between the backface and the nose, wherein a tip of each second cutting element is located in one of a plurality of radial positions, a number of second cutting elements located at a third radial position having a maximum bottom hole depth within the second array being greater than a number of second cutting elements located at a fourth radial position having a lesser bottom hole depth within the second array. 
 
     
     
       2. The drill bit of  claim 1 , further comprising a non-intermesh region adjacent to the backface and an intermesh region between the non-intermesh region and the nose, at least one of the first array or the second array being within the intermesh region. 
     
     
       3. The drill bit of  claim 1 , at least one of the first array or the second array being, when viewed in a rotated bottomhole profile, inboard with respect to radial positions on the cone having the maximum bottom hole depth and the cutting elements at the first and third radial positions being farther outboard with respect to the bit axis than the cutting elements at the second and fourth radial positions. 
     
     
       4. The drill bit of  claim 1 , the first array including at least five distinct radial positions, and at least three cutting elements of the first array being at a same radial position. 
     
     
       5. The drill bit of  claim 1 , a radial spacing between differing, adjacent radial positions within the first array or the second array being the same. 
     
     
       6. The drill bit of  claim 1 , a radially-outermost radial position and a next radially inward radial position within a radius of the first array having a first radial spacing, and a radially-innermost radial position and a next radially outward radial position within the radius of the first array have a second radial spacing, the first radial spacing being less than the second radial spacing. 
     
     
       7. The drill bit of  claim 1 , a number of first cutting elements in a fifth radial position located between the first radial position and the second radial position being less than the number of first cutting elements located at the first radial position and greater than the number of first cutting elements located at the second radial position. 
     
     
       8. The drill bit of  claim 1 , a number of first cutting elements in a fifth radial position located between the first radial position and the second radial position being equal to the number of first cutting elements located at the first radial position. 
     
     
       9. The drill bit of  claim 1 , the first array of first cutting elements being coupled to the first cone and the second array of second cutting elements being coupled to the second cone. 
     
     
       10. A drill bit for drilling through earthen formations and forming a wellbore, the drill bit comprising:
 a bit body having a bit axis; 
 a plurality of cones coupled to the bit body, each cone having a backface, a nose opposite the back face, and a cone axis of rotation, and 
 an array of cutting elements between the backface and the nose of at least one of the plurality of cones, the cutting elements being located at radial positions defined by a radial distance from the bit axis and a bottom hole depth relative to the bit axis, a first spacing between a first radial position within the array having a greatest bottom hole depth and a second radial position adjacent the first radial position being less than a second spacing between a third radial position within the array having a least bottom hole depth and a fourth radial position adjacent the third radial position. 
 
     
     
       11. The drill bit of  claim 10 , the first and second radial positions being within a higher impact load area in the array and the third and fourth radial positions being within a lower impact load area in the array. 
     
     
       12. The drill bit of  claim 10 , the first radial position being the farthest outboard radial position within the array and the third radial position being the farthest inboard radial position within the array. 
     
     
       13. The drill bit of  claim 10 , further comprising a third radial spacing between adjacent radial positions that are located between the second radial position and the fourth radial position, the third spacing being equal to the second spacing. 
     
     
       14. The drill bit of  claim 10 , a radial distance between remaining adjacent cutting elements gradually increasing between the first radial position and the third radial position. 
     
     
       15. The drill bit of  claim 10 , the first radial distance being within a range of from 0 to D/(2*(N−1)), where D is a distance from a farthest outboard radial position within the array to a farthest inboard radial position within the array, and N is a number of positions within the array. 
     
     
       16. The drill bit of  claim 10 , each of the cutting elements in the array including a cutting surface, and at least some of the cutting surfaces, when viewed in rotated bottomhole profile, being more level with a horizontal that is perpendicular to the bit axis than is a wellbore profile in the rotated bottomhole profile view of the array. 
     
     
       17. The drill bit of  claim 10 , the array of cutting elements being a first array of cutting elements in a first band of the at least one of the cones, the drill bit further comprising a second array of cutting elements in a second band of the at least one of the cones, the second band being axially spaced from the first band, each of the cutting elements of the second array having cutting surfaces with different extension heights such that the cutting surfaces of the cutting elements of the second array are more level with a horizontal than a spline formed through cutting surfaces of cutting elements mounted to each of the other cones of the plurality of cones in a rotated profile view. 
     
     
       18. A drill bit for drilling through earthen formations and forming a wellbore, the drill bit comprising:
 a bit body having a bit axis; 
 a plurality of cones coupled to the bit body, each cone having a backface, a nose opposite the back face, a heel surface adjacent the backface, and a generally conical surface between the heel surface and the nose, and a cone axis of rotation; and 
 an array of cutting elements coupled to the generally conical surface of at least one of the cones, the array of cutting elements including cutting elements in at least two different radial positions, each of the at least two different radial positions including a radial distance from the bit axis and a bottom hole depth relative to the bit axis, the cutting elements of the array including cutting surfaces having cutter axes that, when viewed in rotated bottomhole profile, have a non-uniform spacing, and the spacing between cutter axes of cutter surfaces closer to a horizontal line tangent to a spline of the cutting surfaces in the bottomhole profile being less than the spacing between cutter axes of cutting surfaces farther from the horizontal line. 
 
     
     
       19. The drill bit of  claim 18 , the cutter surfaces closer to the horizontal line corresponding to:
 a cutting element at a farthest radially-outward position within the array and a next inward cutting element, and the cutter surfaces farther from the horizontal line corresponding to a cutting element at a farthest radially-inward position within the array and a next outward cutting element; or 
 a farthest inboard position with respect to the bit axis and a next outboard cutting element, and the cutter surfaces farther from the horizontal line corresponding to a cutting element at a farthest outboard position with respect to the bit axis and a next inboard cutting element. 
 
     
     
       20. The drill bit of  claim 18 , wherein:
 a spacing between adjacent cutter axes closer to a bottom of a wellbore within the bottomhole profile is less than a spacing between adjacent cutter axes farther away from the bottom of the wellbore within the bottomhole profile; 
 at least two of the cutting elements are at a same radial position and have aligned cutter axes; and; 
 at least one of the cutting surfaces deviates from the spline when viewed in rotated bottomhole profile.